The act of greeting someone by gentlysqueezing (and hence exciting, and possibly putting a smile on) their nipple. Usually followed by a wink. Not recommended for greeting someone of the opposite gender, but results do vary.

Every time I see Billy, he nippleshakes me but I never get the time to do it back because I would lose all my senses for a couple of seconds.

James tried to nippleshake that girl he had a crush on. He thought it would have a similar effect to when I do it to him. He was wrong. Now he has a bruise on his right cheek to tell the story.